The inventive concept relates to a semiconductor memory device. More particularly, the inventive concept relates to a vertical or three-dimensional (3D) semiconductor memory device.
In order for semiconductor devices to offer excellent performance and yet remain low in cost to produce, it is necessary for the semiconductor devices to have a high degree of integration. In particular, the integration degree of a semiconductor memory device is an important factor in determining the price of an electronic product having such a memory. The integration degree of a two-dimensional memory device is mainly a factor of the region occupied by a unit memory cell. Hence, the integration degree of a two-dimensional memory device may be significantly affected by the technical level attainable in a technique of forming a fine pattern.
However, equipment for forming fine patterns is extremely expensive. Furthermore, although the integration degree of two-dimensional memory devices has been increased throughout the years, it is still limited. Therefore, semiconductor memory devices having a three-dimensional structure are being developed to provide memory devices of higher degrees of integration at reasonable costs.